Means for shielding sound detector and amplifier apparatus



Nov. 27, 1928. 1,693,072

L. DE FOREST MEANS FOR smswme SOUND DETECTOR AND AMPLIFIER APPARATUS Filed April 28, 1923 ATTORNEYS 3 Patented Nov. 27; 1928.

UNITED STATES PATENT OFFICE.

LEE DE FOREST, OF NEW YORK, N. Y., ASSIGNOB TO DE FOREST PHONOFILM CORPORA- TION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

MEAN S FOR SHIELDING SOUND DETECTOR AND AMPLIFIER APPARATUS.

Application filed April 28, 1923. Serial No. 635,337.

This invention relates to means for shielding sound detectors and high tension amplifying apparatus from disturbances due to elect'ro-magnetic or electrostatic disturbances.

The object of the invention is to provide means of this character which is simple in structure, efficient in operation and economical in manufacture.

Further objects'of the invention will appear more fully hereinafter.

- The invention consists substantially in the construction, combination, location and relative arrangements of parts, all as will be more fully hereinafter set forth as shown in the accompanying drawing, and will be more fully outlined 1n the appended'claims.

Referring to the drawing the single fig ure represents the means embodying my invention for shielding a sound detector and amplifyin apparatus from extraneous elec-.

tric distur ances.

Referring to the drawing, reference characters 1 and 2 designate microphones or the like, for example of the carbon granular electrostatic electro-magnetic type, thermo or ionic type. In other words, the microphones are diagrammatically illustrated, and may be of any standard or desired type, and I do not desire to be limited or. restricted in this respect.

It is frequently of advantage to use two or more sets of microphones, either screwed together or scattered about the room where the sound waves are being picked rp. I have shown in the illustration two su h microphones grouped together, but I to not desire to be limited or restricted in this respect. Each microphone or group of microphones, in accordance with my invention, is enclosed in an open mesh metallic casing 3, and the wires leading to the microphones are encased in metallic conduits, sheaths or the like, 4:, which is in electrical contact with the enclosing mesh case 3. The mesh case 3 thus forms a complete shield against electrostatic and electro-magnetic induction, and at the same time allows the sound waves to pass freely therethrough to the micro-- phones.

Reference numeral 5 designates an ampli- I of them is thus made possible.

for, The sheaths 4 for the connecting wire is in contact with the metal case 6, and the cage 3, and the metal case 6 when used is outlay wires from the amplifying appara tus are illustrated at 8.

It will be understood that the cage 3 and the case 6 are both grounded. Inasmuch as the sheath l is in metallic contact with both cage 3 and case 6, it is likewise grounded. Where the cage 3 and the case 6 are employed together a common ground for both It Will be understood, however, that when the cage 3 is employed alone, a separate ground connection is supplied therefor. Many changes and modifications will read- 11y occur to those skilled in the art Without departing from the spirit and scope of my nvention, as defined in the claims; but havmg now set forth the objects and nature of my invention and having shown and described a structure embodying the principles thereof, what I claim is new and useful and of my own invention, and desire to secure by Letters Patent is 1. The combination with a microphone device, of means'immediately associated with said device for shielding said device against electrical disturbances while \allowing free access thereto by sound waves.

2. The combination with a microphone device of a metallic shield immediately associated with said device which offers neglible opposition to sound-waves, and a ground connection for said shield.

3. The combination with a microphone device, of a wire cage immediately enclosing said device, and a ground connection for said cage.

4. The combination with a microphone device, of amplifying apparatus electrically connected thereto, of means for shielding said device, and said a paratus and their connection against electrical disturbances.

5. The combination with a microphone device, of amplifying apparatus electrically connected thereto, of a metallic shield for said device, apparatus and connection for shielding the same against electr1cal dis- 1turhances and a ground connection there- -or.

6. The combination with a microphone device, of amplifying apparatus electrically connected thereto, of a metallic shield for said device, apparatus and connection for shielding the same against electrical disturhances, said shields being in metallic con tact with each other, and a common ground connection for said shields. 10

In testimony whereof I have hereunto set my hand on this 25th day of April A. D., 1923.

LEE DE FOREST. 

